This invention relates to a method of simultaneously applying a coating of uniform thicknesses to two or more surfaces of a structural member, such as an I-beam or the like. More particularly, this invention is concerned with a method of for applying a uniform layer of a spreadable, hardenable-in-place fire-proofing or thermal protection material to a structural beam or the like of a building or other structure.
Many cities and states require that the structural members in larger buildings and other structures have a fire resistant thermal coating applied thereto to prevent or delay weakening of the member in the event of a fire and to thus preserve the structural integrity of the building. Several suitable fire barrier materials are commercially available, but this invention particularly concerns itself with the method of and apparatus for applying cementitious, hardenable-in-place fire-proofing materials, such as are commercially available from the assignee of this invention, the Carboline Company of St. Louis, Missouri, under their registered trademark PYROCRETE 102. It will be understood that other fire-proofing materials, such as concrete or gunite may also be applied by the method of and apparatus for this invention. Generally, these cementitious fire-proofing materials are spreadable on surfaces of a structural member to be protected and are allowed to harden or cure so as to form a plasterlike coating on the member. In the event of a fire, PYROCRETE 102 fire-proofing material undergoes a thermohydrogenation reaction during which water vapor is released thus enhancing the thermal protection to the member. The thickness of the fire-proofing coating is critical because if a specified minimum thickness is not maintained, even over a small area of the member, insufficient thermal protection will be afforded to the member and the overall fire rating of the beam may be markedly decreased. If excess material is applied, waste of the fire-proofing material will result.
Heretofore, fire-proofing material was either sprayed or manually spread (e.g., trowelled) onto the surfaces of the beam (or other member). Measurements were frequently taken by means of inserting a probe into the freshly applied fire-proofing material so as to insure that the desired thickness was applied. In instances where a more uniform and aesthetically pleasing appearance was desired, manual trowelling rather than spraying of the material onto the surfaces was required. The speed at at which the fire-proofing material could be applied and the uniformity of the finish was dependent upon the skill of the workman trowelling the material onto the beam. In applying the spreadable fire-proofing material to vertical columns and structural beams, it was sometimes difficult for a workman to gain access to all surfaces of the members for the purpose of manually trowelling the fire-proofing material thereon.
Other methods of applying fire-proofing coating to beam surfaces are known in which form boards sized to the thickness of the coating to be applied were secured to the flange edges of an I-beam. Excess material was then applied to the beam surfaces and a screed or other tool was run along the edges of the form boards to strike off excess material from one surface of the beam in much the same manner as a screed in run along a concrete form to strike excess concrete. Other surfaces of the beam were then similarly finished and the form boards were then removed. Additional insulation material was added to fill in the spaces vacated by the form boards. This prior screed method, however, required that the form boards be accurately sized to the thickness of the material to be applied, and to the dimensions of the beam. This method did not allow multiple surfaces of the beam to be simultaneously finished and the finishing of the inner flange and web surfaces of the beam was still essentially a manual trowelling operation.